Diabetic retinopathy (DR) is a common microvascular complication of diabetes. It occurs in nearly all patients with type 1 diabetes and over 60% of patients with type 2 diabetes during the first two decades of disease. The major pathological factors of DR include local inflammation with hypercytokinemia, retinal infiltration with immune cells, uncontrolled neovascular growth penetrating the retina, and retinal vascular leakage that leads to vision loss. All of these pathologies are related to vascular dysfunction and can be impacted by multiple pro-inflammatory and pro-angiogenic signals such as IL-1, TNFa, DAMPs, VEGF and WNTs. However, anti-VEGF biologics, which is the current pharmacological standard-of-care, improves visual acuity in less than half of the patient population. This failure n efficacy is commonly ascribed to functional redundancy between VEGF and other DR- related pathogenic factors and suggests a need for a drug that can block multiple DR-related signaling pathways. We have identified a small GTPase ARF6 is over-expressed in diabetic human and mouse eyes. Inhibition of ARF6 reduces IL-1- and VEGF-induced retinal permeability and neovascularization in OIR. Published and our unpublished data have also shown that activated ARF6 plays a critical role in IL-1, TNFa and VEGF signaling in endothelial cells and WNT signaling in cancer cells. These results suggest that ARF6 is a convergence point for many DR-related inflammatory, angiogenic, and WNT pathways and is a key player in the pathologic progression of DR. We therefore hypothesize that inhibiting ARF6 activation will reduce vascular permeability and neovascularization and their debilitating sequelae. To test this hypothesis, we will pursue two aims. In Aim 1, we will determine whether endothelial expression of Arf6 is required for the development and/or progression of diabetic retinopathy by assessing pathologic responses in endothelial-specific Arf6 knockout mice using oxygen induced retinopathy (OIR) and streptozotocin (STZ)-induced diabetic mouse models. We will also determine whether the results from this genetic model are phenocopied in wild-type mice treated with the ARF6 small molecule inhibitor, NAV2729. In Aim 2, we will examine how universal the activation of ARF6 may be in controlling DR-related pathologic signaling pathways and will also define the mechanism by which activated ARF6 controls endothelial permeability or migration. If our hypothesis is correct, ARF6 will become an ideal molecular target for the treatment DR due to the fact that and may overcome many of the current problems with we will determine the role of activated ARF6 in the other retinal cell types and expand our study to other vascular eye diseases.